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b=TIApE0b49DQ54mrZl9FGRFT27M8H798lk0FaGL90qgjp9De/0PAWEdW1B8tHxUbte ROAbQ/6qA/4BP+gYXZ1v/AV90+N4aZaxW3sidFjMf8l2efh5HYPZcYS6+RNaa0mKEN Xvooe5oR7rQoX7S9DzNjxeJCy0823ASF3e6Q2s+GQ7O1n8tw8lgigdGYYoxWZLB/mi AarmBhlA6sgN3TGY1i92003wII0qyhdCnMoka++OIgEIVAO9dyQEX051UNv5eCZ2Ej kLhkrTjSW0oArRLVYpImzg9myioghgTj4F52RXhvMd35vjJbV2juSgT64n/BLfN4pB t1usvPpxtiDtw== Message-ID: <7c1db5ef-2457-46ff-ab20-dd4090570fb6@kernel.org> Date: Mon, 9 Mar 2026 15:15:24 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: prevent droppable mappings from being locked To: Anthony Yznaga , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jannh@google.com, pfalcato@suse.de, Jason@zx2c4.com References: <20260306204550.8405-1-anthony.yznaga@oracle.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: D136540018 X-Stat-Signature: grjtpdjwztghxemzxmeqrghkejg3581h X-Rspam-User: X-HE-Tag: 1773065732-188271 X-HE-Meta: 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 psFeFpHO XXTZAD85rMqDUfyIywfPbRAG6bqgM4E+LeVZ6UVbDkvqtoe5V5Mo/nGOt5vy8/uAsLwcbM7ro55vpfuSkwIHlfJUHvheU2H9CY+lwfRVm5jF/y3/TnnVnzYj7DdNosBLPqwGskw+NvMJxygSYu/vj8Hsm0JP3zwN4n1vv978fEFGxc5LY/RaGVfiiyy/qRQ2+JmpCgy+Jz7of5vKfJfLfXkYsj1zXMTBaE1quh3/hOqgnd15LfIbAHULpCD6hhJHOwa3GRyZpbQCZX8fqIZJMHAI3I15Bi39K+n9M5PScqb0BvkZ4wlW2PPXwsZq5T2WOmDzQ+4LnpxZepXO7/ogtipv2cvabqnSw2auZ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/6/26 21:45, Anthony Yznaga wrote: > Mappings created with MAP_DROPPABLE cannot be locked via mlock() due > to the check in mlock_fixup(). However, they will be locked indirectly > if they are created after mlockall(MCL_FUTURE). > > Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") > Signed-off-by: Anthony Yznaga > --- > include/linux/mm.h | 3 +++ > mm/mlock.c | 4 ++-- > mm/vma.c | 2 +- > 3 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 5be3d8a8f806..bb830574d112 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -574,6 +574,9 @@ enum { > /* This mask represents all the VMA flag bits used by mlock */ > #define VM_LOCKED_MASK (VM_LOCKED | VM_LOCKONFAULT) > > +/* This mask prevents VMAs from being mlock'd */ > +#define VM_NO_MLOCK_MASK (VM_SPECIAL | VM_DROPPABLE) Instead of adding that, could we cleanup further by doing something like the following? The usage of "vma->vm_mm" must be double checked, and we'll have to take care of making the tools/testing/vma test happy. Not even compile tested, so will require some more work. diff --git a/include/linux/hugetlb_inline.h b/include/linux/hugetlb_inline.h index 593f5d4e108b..755281fab23d 100644 --- a/include/linux/hugetlb_inline.h +++ b/include/linux/hugetlb_inline.h @@ -30,7 +30,7 @@ static inline bool is_vma_hugetlb_flags(const vma_flags_t *flags) #endif -static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma) +static inline bool is_vm_hugetlb_page(const struct vm_area_struct *vma) { return is_vm_hugetlb_flags(vma->vm_flags); } diff --git a/mm/internal.h b/mm/internal.h index 6e1162e13289..b70ebbdafe00 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1242,6 +1242,15 @@ static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, } return fpin; } + +static inline bool vma_supports_mlock(const struct vm_area_struct *vma) +{ + if (vma->vm_flags & (VM_SPECIAL | VM_DROPPABLE)) + return false; + if (vma_is_dax(vma) || is_vm_hugetlb_page(vma)) + return false; + return vma != get_gate_vma(vma->vm_mm); +} #else /* !CONFIG_MMU */ static inline void unmap_mapping_folio(struct folio *folio) { } static inline void mlock_new_folio(struct folio *folio) { } diff --git a/mm/mlock.c b/mm/mlock.c index 1a92d16f3684..e16b2ea234f7 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -472,9 +472,7 @@ static int mlock_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma, int ret = 0; vm_flags_t oldflags = vma->vm_flags; - if (newflags == oldflags || (oldflags & VM_SPECIAL) || - is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) || - vma_is_dax(vma) || vma_is_secretmem(vma) || (oldflags & VM_DROPPABLE)) + if (newflags == oldflags || !vma_supports_mlock(vma)) /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */ goto out; diff --git a/mm/vma.c b/mm/vma.c index e95fd5a5fe5c..b7055c264b5d 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2589,9 +2589,7 @@ static void __mmap_complete(struct mmap_state *map, struct vm_area_struct *vma) vm_stat_account(mm, vma->vm_flags, map->pglen); if (vm_flags & VM_LOCKED) { - if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) || - is_vm_hugetlb_page(vma) || - vma == get_gate_vma(mm)) + if (!vma_supports_mlock(vma)) vm_flags_clear(vma, VM_LOCKED_MASK); else mm->locked_vm += map->pglen; -- 2.43.0 -- Cheers, David